Vertical power unit and outboard engine system

ABSTRACT

A vertical power unit includes: an engine having a vertically arranged crankshaft; a vertically arranged output shaft provided below the crankshaft; and a torque converter providing a connection between the crankshaft and the output shaft. The torque converter is arranged so as to be offset from the crankshaft toward a cylinder block of the engine. A transmission device is provided between the crankshaft and the torque converter. The output shaft is arranged coaxially with the torque converter. Thus, the center of gravity of the vertical power unit is positioned as close as possible to the central portion of the engine, thereby minimizing bias of the center of gravity due to the weight of the torque converter and the output shaft to facilitate the handling of the vertical power unit.

RELATED APPLICATION DATA

The present invention is based upon Japanese priority application No.2006-145962, which is hereby incorporated in its entirety herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improvement of a vertical power unitcomprising: an engine which has a vertically arranged crankshaft; avertically arranged output shaft provided below the crankshaft; and atorque converter which is disposed between the crankshaft and the outputshaft, and transmits power from the crankshaft to the output shaft. Thepresent invention also relates to an improvement of an outboard enginesystem comprising: a casing coupled to a swivel case via a swivel shaft;an engine mounted in an upper part of the casing such that a crankshaftof the engine is vertically arranged and a cylinder block of the enginefaces in a direction opposite to the swivel shaft; a torque converter; avertically arranged output shaft connected to the crankshaft through thetorque converter; a horizontally arranged propeller shaft provided belowthe output shaft; and a forward-reverse shifting gear mechanism forproviding a connection between the output shaft and the propeller shaft;the torque converter, the output shaft, the propeller shaft and theforward-reverse shifting gear mechanism being disposed in the casing.

2. Description of the Related Art

Such an outboard engine systems is already known as disclosed in U.S.Pat. No. 3,407,600.

In the vertical power unit or outboard engine system disclosed in U.S.Pat. No. 3,407,600, although a crankshaft of an engine is arranged so asto be largely apart from the central portion of the engine toward oneside, an output shaft and a torque converter having relatively largeweight are arranged immediately below and coaxially with the crankshaft,and thus the center of gravity of the vertical power unit or outboardengine system is biased further toward the crankshaft, whereby it isdifficult to handle the torque converter or the output shaft.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above problem,and has an object to provide a vertical power unit which is easilyhandled by minimizing bias of the center of gravity due to the weight ofa torque converter and a output shaft.

In order to achieve the above object, according to a first feature ofthe present invention, there is provided a vertical power unitcomprising: an engine which has a vertically arranged crankshaft; avertically arranged output shaft provided below the crankshaft; and atorque converter which is disposed between the crankshaft and the outputshaft, and transmits power from the crankshaft to the output shaft,wherein the torque converter is arranged so as to be offset from thecrankshaft toward a cylinder block of the engine; a transmission deviceis provided between the crankshaft and the torque converter; and theoutput shaft is arranged coaxially with the torque converter.

With the first feature of the present invention, because the outputshaft and the torque converter having relatively large weight are offsetby a certain distance from the crankshaft toward the cylinder block, thecenter of gravity of the vertical power unit is arranged closer to thecentral portion of the engine, thereby facilitating the handling of thevertical power unit. Further, the power of the crankshaft is transmittedto the torque converter via the transmission device without any trouble.

According to a second feature of the present invention, in addition tothe first feature, the vertical power unit further comprises an oilreservoir case provided between the transmission device and the torqueconverter to receive a lubrication oil flowing down from the engine forlubricating the transmission device.

With the second feature of the present invention, because the oilreservoir case which houses the transmission device receives the oilhaving completed the lubrication of each portion of the engine, the oilcan be also used for lubrication of the transmission device to securethe durability of the transmission device.

According to a third feature of the present invention, in addition tothe second feature, the vertical power unit further comprises: an oiltank provided below the torque converter to store oil which is suppliedto the engine; and an oil passage provided apart from the torqueconverter so as to return the oil in the oil reservoir case to the oiltank.

With the third feature of the present invention, the oil in the oilreservoir case returns to the oil tank without contact with an outerperipheral surface of the torque converter, thereby avoiding needlessagitation and splash of the oil to minimize the power loss.

According to a fourth feature of the present invention, there isprovided an outboard engine system comprising: a casing coupled to aswivel case via a swivel shaft; an engine mounted in an upper part ofthe casing such that a crankshaft of the engine is vertically arrangedand a cylinder block of the engine faces in a direction opposite to theswivel shaft; a torque converter; a vertically arranged output shaftconnected to the crankshaft through the torque converter; a horizontallyarranged propeller shaft provided below the output shaft; and aforward-reverse shifting gear mechanism for providing a connectionbetween the output shaft and the propeller shaft; the torque converter,the output shaft, the propeller shaft and the forward-reverse shiftinggear mechanism being disposed in the casing, wherein the torqueconverter is arranged so as to be offset from the crankshaft toward acylinder block of the engine; a transmission device is provided betweenthe crankshaft and the torque converter; and the output shaft isarranged coaxially with the torque converter.

With the fourth feature of the present invention, because the outputshaft and the torque converter having relatively large weight are offsetby a certain distance from the crankshaft toward the cylinder block, thecenter of gravity of the outboard engine system is arranged closer tothe central part of the engine in the front-rear direction, therebyfacilitating the handling of the outboard engine system. Especially thearrangement in which the torque converter and the output shaft areoffset by a certain distance from the crankshaft toward the cylinderblock means that the crankshaft is offset from the torque converter andthe output shaft toward the swivel shaft. Thus, the center of gravity ofthe engine correspondingly gets closer to the swivel shaft, therebyproviding a smooth steering of the outboard engine system about theswivel shaft.

Further, the power of the crankshaft is transmitted to the torqueconverter via the transmission device without any trouble.

The above-mentioned object, other objects, characteristics, andadvantages of the present invention will become apparent from apreferred embodiment, which will be described in detail below byreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing an outboard engine system according to anembodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the portion 2 of FIG. 1.

FIG. 3 is an enlarged view showing the essential portions of FIG. 2.

FIG. 4 is an enlarged sectional view showing the portion 4 of FIG. 1.

FIG. 5 is a view showing a hydraulic circuit including an oil pump.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, an outboard engine system O includes a casing 1 which has awater-cooled multi-cylinder four-stroke engine E mounted in its upperportion, and supports a propeller shaft 3 at its lower portion. Thepropeller shaft 3 has a propeller 2 provided at its rear end. Avertically-extending swivel shaft 6 is mounted to the casing 1 via anupper arm 4 and a lower arm 5 so as to situate in front of the casing 1.The swivel shaft 6 is rotatably supported by a swivel case 7 which iscoupled to a stern bracket 8 via a horizontally-extending tilt shaft 9.The stern bracket 8 is cramped to a transom Bt of a body of a ship.Therefore, the casing 1 is horizontally rotatable around the swivelshaft 6, and vertically tiltable around the tilt shaft 9. The referencenumeral Ef denotes a removable engine hood for covering the engine E.

In FIG. 2, FIG. 3 and FIG. 4, the above casing 1 includes the extensioncase 10, the mount case 11 bolt-coupled to an upper end of the extensioncase 10, and a gear case 12 bolt-coupled to a lower end of the extensioncase 10. The extension case 10 includes an upper case 10 a and a lowercase 10 b bolt-coupled to the upper case 10 a. The mount case 11 isbolt-coupled to an upper end surface of the upper case 10 a.

The casing 1 further includes annular lower distance members 13, anbearing bracket 14, and annular upper distance members 15, which aresequentially superimposed on the upper end of the mount case 11. Theengine E is mounted to the upper distance member 15 with the crankshaft17 being vertically arranged and the cylinder block 18 facing rearward.The bearing bracket 14 and upper distance member 15 are secured to thecylinder block 18 and a bottom wall of the crankcase 19 of the engine Eby a plurality of bolts 16 ₁. The lower distance member 13, the bearingbracket 14, and the upper distance member 15 are secured to one anotherby a plurality of bolts 16 ₂.

In FIG. 2 and FIG. 3, a transmission device 81 is arranged in an oilreservoir case 24 so as to be connected to the crankshaft 17; a torqueconverter T is vertically arranged in the annular upper distance member15 so as to be connected to the transmission device 81; and an outputshaft 20 is vertically arranged in the extension case 10 so as beconnected to the torque converter T. In this structure, the torqueconverter T is arranged so that its axis is offset by a certain distancee from the crankshaft 17 toward the cylinder block 18, and the outputshaft 20 is arranged on the axis line of the torque converter T.

The gear case 12 horizontally supports the propeller shaft 3 having thepropeller 2 at its rear end, and houses a forward-reverse shifting gearmechanism 21 connecting the propeller shaft 3 to the output shaft 20.

In operation of the engine E, the power thereof is transmitted from thecrankshaft 17 to the output shaft 20 via the transmission device 81 andthe torque converter T, and further to the propeller shaft 3 via theforward-reverse shifting gear mechanism 21, thereby driving thepropeller 2. The rotational direction of the propeller 2 is controlledand switched by the forward-reverse shifting gear mechanism 21.

In the extension case 10, an oil tank 22 open to the mount case 11 isintegrally formed with the upper case 10 a of the extension case 10. Theoil tank 22 stores oil 23 which is used in both lubrication of theengine E and operation of the torque converter T. A downstream end 90 ofan exhaust gas passage of the engine E is integrally formed with theupper case 10 a.

As clearly shown in FIG. 3, the transmission device 81 comprises a drivegear 81 a and a follower gear 81 b. The drive gear 81 a is securethrough a plurality of bolts 82 to a lower end of the crankshaft 17. Thefollower gear 81 b is supported by a ball bearing 84 at a positionoffset by the certain distance e from an axis of the crankshaft 17toward the cylinder block 18, and is engaged with the drive gear 81 a.The follower gear 81 b integrally has an axis portion which passesthrough a bottom wall of the oil reservoir case 24. A drive plate 31having a diameter larger than that of the torque converter T is securedto a lower end of the axis portion of the follower gear 81 b by aplurality of bolts 32 ₂. An oil seal 85 is mounted to the oil reservoircase 24 so as to closely contact an outer peripheral surface of the axisportion.

The torque converter T includes a pump impeller 25, a turbine runner 26arranged above the pump impeller 25 and opposed to the pump impeller 25,a stator 27 arranged between the inner peripheral portions of the pumpimpeller 25 and the turbine runner 26, and a circulation circuit 28 ofworking oil which is defined between these three impellers 25 to 27. Thepump impeller 25 integrally includes a transmission cover 29 forcovering an upper surface of the turbine runner 3. A ring gear 30 forstarting operation is secured to an outer peripheral surface of thetransmission cover 29. The ring gear 30 is secured to the drive plate 31by a plurality of third bolts.

A cup-shaped supporting cylinder 34 is secured to a central part of thetransmission cover 29. The supporting cylinder 34 is fitted into asupporting hole 33 which is open to the central part of the lower endsurface of the follower gear 81 b. The output shaft 20 has an upper endwhich extends to the inside of the supporting cylinder 34 and issupported in the supporting cylinder 34 via a bearing bush 35. A hub ofthe turbine runner 26 is spline-coupled to the output shaft 20. A hollowstator shaft 37 is arranged around the outer periphery of the outputshaft 20 so as to be supported by the output shaft 20 via a needlebearing 36. A known free wheel 38 is interposed between the stator shaft37 and a hub of the stator 27.

As described above, the torque converter T is arranged so that its axisis offset by the certain distance e from the crankshaft 17 toward thecylinder block 18, and the output shaft 20 is arranged on the axis lineof the torque converter T. Thus, the engine E, the transmission device81, the torque converter T, and the output shaft 20 constitute thevertical power unit.

A hollow pump shaft 39 is arranged at the outer periphery of the statorshaft 37. The hollow pump shaft 39 is integrally coupled to the pumpimpeller 25 and extends downward. The pump shaft 39 is supported by thebearing bracket 14 via an upper ball bearing 43 on the side of the outerperiphery. An oil pump 41 driven at the lower end portion of the pumpshaft 39 is attached to a pump housing 40 formed at a lower surface ofthe bearing bracket 14. A pump cover 42 covering a lower surface of theoil pump 41 is bolt-coupled to a lower surface of the bearing bracket14. An oil seal 45 is attached to an upper end portion of the bearingbracket 14 such that its lip is in close contact with an outerperipheral surface of the pump shaft 39 at a position immediately abovethe ball bearing 43.

The stator shaft 37 has a large diameter portion 37 a at its lower end.A flange 37 b is integrally formed on an outer periphery of the largediameter portion 37 a. The flange 37 b is secured to the pump cover 42by a bolt 46. A lower ball bearing 44 is mounted to its inner peripheryof the flange 37 b so as to support the output shaft 20.

A thrust needle bearing 47 is interposed between the pump impeller 25and the hub of the stator 27. A thrust needle bearing 48 is interposedbetween the hub of the turbine runner 26 and the transmission cover 29.

The oil pump 41 draws up the oil stored in the oil tank 22, and suppliesthe oil to the engine E and the torque converter T. The route of the oildischarged by the oil pump 41 will be described below with reference toFIG. 5.

The oil pump 41 draws up the oil 23 stored in the oil tank 22 via an oilsuction passage 50, and discharges the oil 23 to a first oil supplypassage 51. The oil discharged to first oil supply passage 51 isfiltered by an oil filter 53 provided in the middle of the first oilsupply passage 51, and supplied to a lubricated portion of the engine E.After the lubrication, the oil flows downward to the bottom portion ofthe crankcase 19 of the engine E, and returns to the oil tank 22 via thefirst oil return passage 59.

The oil discharged to the first oil supply passage 51 is also suppliedto a circulation circuit 28 of the torque converter T via a second oilsupply passage 52 which is a branch from the first oil supply passage 51upstream of the oil filter 53. After being used in the circulationcircuit 28, the oil is returned to the oil suction passage 50 or the oiltank 22 via a second oil return passage 54.

An oil relief passage 55 is another branch from the first oil supplypassage 51 upstream of the oil filter 53, and reaches the oil suctionpassage 50. The oil relief passage 55 has a pressure relief valve 56which opens when an oil pressure of the first oil supply passage 51exceeds a specified value.

The second oil supply passage 52 has an orifice 57 for controlling theamount of the oil supplied to the circulation circuit 28 of the torqueconverter T. The second oil return passage 54 also has a normally-closedpressure response valve 58 which opens when an oil pressure upstream ofthe second oil return passage 54 exceeds a predetermined value.

Thus, when the pressure of the first oil supply passage 51 is regulatedby the single pressure relief valve 56, the pressure of the second oilsupply passage 52 is concurrently regulated, whereby the pressure of thecirculation circuit 28 in the torque converter T is regulated, and thetransmission characteristics of the torque converter T can bestabilized. In addition, the downstream end of the oil relief passage 55is connected to the oil suction passage 50, whereby the oil releasedfrom the oil relief passage 55 is smoothly returned to the oil pump 41,thereby simplifying the oil pressure circuit.

Referring again to FIG. 2 and FIG. 3, the oil suction passage 50 issuspended from the bearing bracket 14, and includes a suction tube 50 ahaving a lower end portion extending into the oil tank 22, and a lateraloil passage 50 b which is provided in the bearing bracket 14 so as tocommunicate the upper end portion of the suction tube 50 a with asuction port 41 a of the oil pump 41.

The second oil supply passage 52 includes a bottomed vertical hole 52 bwhich is provided at a central portion of the output shaft 20 so as toopen in the upper end surface of the output shaft 20, an inlet oilpassage 52 a which is provided to pass through the fitted portionsbetween the pump cover 42, the stator shaft 37 and the output shaft 20so as to communicate a discharge port 41 b of the oil pump 41 with thelower portion of the vertical hole 52 b, and a horizontal hole 52 cwhich is provided at an upper part of the vertical hole 52 b so as topass through the peripheral portion of the thrust needle bearing 48 intothe transmission cover 29. The interior of the transmission cover 29communicates with an outer peripheral portion of the circulation circuit28.

The second oil return passage 54 includes a cylindrical oil passage 54 awhich is defined between the output shaft 20 and the stator shaft 37 andis in communication with the circulation circuit 28 through theperipheral portion of the thrust needle bearing 47 above the hub of thepump impeller 25, and a lateral outlet oil passage 54 b which isprovided at the pump cover 42 to communicate with the lower end portionof the cylindrical oil passage 54 a. The outlet oil passage 54 b is incommunication with the lateral oil passage 50 b via the pressureresponse valve 58.

The pressure response valve 58 includes a cylindrical valve chamber 60horizontally provided in the pump cover 42, and a piston-type valve body61 slidably fitted in the valve chamber 60. The outlet oil passage 54 bis open to the inner end surface of the valve chamber 60. A valve hole62 is open in the inner side surface of the valve chamber 60 so as tocommunicate with the lateral oil passage 50 b or the oil tank 22. Thevalve body 61 is arranged so that its top surface, that is, pressurereceiving surface is directed toward the outlet oil passage 54 b. Thevalve hole 62 is closed when the valve body 61 is advanced toward theoutlet oil passage 54 b, and is opened when the valve body 61 isretracted. A valve spring 63 is arranged between the rear surface of thevalve body 61 and the screw plug 64 screwed into the opening of thevalve chamber 60 so as to urge the valve body 61 to the advancingdirection, that is, to the valve closing direction. Therefore, the valvebody 61 is normally held at its closed position by a set load of thevalve spring 63 to thereby block the second oil return passage 54. Whenan oil pressure is generated upstream of the second oil return passage54 and exceeds a predetermined value, the top surface of the valve body61 receives the oil pressure, and the valve body 61 is caused to retractagainst the set load of the valve spring 63 to be opened, whereby thesecond oil return passage 54 enters a communicated state.

An opening 66 (see FIG. 2) is provided in a bottom wall of the crankcase19 of the engine E. The oil having completed the lubrication of theengine E is discharged through the opening 66 into the oil reservoircase 24. A series of vertical through holes 67 are formed in outerperipheral portions of the oil reservoir case 24, and the upper distancemember 15 and the bearing bracket 14 which are attached to the oilreservoir case 24. The through holes 67 cause the interior of the oilreservoir case 24 to be opened to a space above the mount case 11. Themount case 11 has an opening 68 which is open to the oil tank 22.Therefore, the oil which resides on the bottom portion of the crankcase19 after completing the lubrication of the engine E, first moves fromthe opening 66 into the oil reservoir case 24 to lubricate thetransmission device 81, and then returns to the oil tank 22 via thethrough holes 67 and the opening 68. The opening 66, the through holes67, and the opening 68 form the first oil return passage 59.

In FIG. 3, a first seal member 70 ₁ is attached to the outer peripheryof the stator shaft 37 so as to closely contacts the inner peripheralsurface of the pump shaft 39 in a relatively rotatable manner, therebypreventing the oil in the torque converter T from flowing downward ofthe pump shaft 39.

A second seal member 70 ₂ is provided between the stator shaft 37 andthe pump cover 42 at a position below the inlet oil passage 52 a,thereby preventing the oil in the inlet oil passage 52 a from flowingdownward of the stator shaft 37 and the pump cover 42.

Third and fourth seal members 70 ₃ and 70 ₄ are provided around theouter periphery of the output shaft 20 in the fitted portions of theoutput shaft 20 and the stator shaft 37 such that they are arranged inthe vertical direction to closely contact from above and below the innerperipheral surface of the stator shaft 37 in a relatively rotatablemanner. The third and fourth seal members 70 ₃ and 70 ₄ cooperate toprevent the oil in the inlet oil passage 52 a from flowing out of thefitted portions of the output shaft 20 and the stator shaft 37. Further,the upper seal member 70 ₃ prevents the oil in the inlet oil passage 54a from flowing downward to the fitted portions of the output shaft 20and the stator shaft 37.

As shown in FIG. 3 and FIG. 4, the output shaft 20 is divided into anupper output shaft 20 a having the vertical hole 52 b and supported bythe lower ball bearing 44, and a lower output shaft 20 b coupled to theforward-reverse shifting gear mechanism 21 (see FIG. 1). An upper endportion of the lower output shaft 20 b is supported via a bush 72 in asupporting sleeve 71 which is integrally formed with the outer side ofthe oil tank 22. The upper output shaft 20 a has a flange 73 which abutson the upper end surface of an inner lace of the ball bearing 44attached to the inner periphery of the large diameter portion 37 a ofthe stator shaft 37. A stopper collar 74 is locked to the innerperipheral surface of the large diameter portion 37 a so as to supportthe lower end surface of an outer lace of the ball bearing 44.Therefore, unless the stopper collar 74 is removed, the upper outputshaft 20 a cannot be pulled out downward from the central portion of thetorque converter T.

Besides the vertical hole 52 b, the upper output shaft 20 a has a plughole 76 connected to the lower end of the vertical hole 52 b, and aspline hole 77 connected to the lower end of the plug hole 76 and openin the lower end surface of the upper output shaft 20 a. A plug 78 isscrewed into the plug hole 76 to form the bottom wall of the verticalhole 52 b. The plug 78 has a part of the inlet oil passage 52 a, and theorifice 57 for communicating the inlet oil passage 52 a with thevertical hole 52 b. A fifth seal member 70 ₅ is attached to the plug 78to closely contact the inner peripheral surface of the plug hole 76.

The inlet oil passage 52 a may be formed to bypass the plug 78.

A spline shaft 80 is formed at the upper end portion of the lower outputshaft 20 b. The spline shaft 80 is fitted into the spline hole 77 tocouples the upper and lower output shafts 20 a and 20 b to each other.

Now, operation of the first embodiment will be described below.

In operation of the engine E, its power is transmitted from thecrankshaft 17 through the drive gear 81 a and the follower gear 81 b tothe drive plate 31 and the pump impeller 25, thereby driving the pumpimpeller 25, and also driving the oil pump 41 through the pump shaft 39.The thus-driven oil pump 41 draws up the oil 23 in the oil tank 22through the oil suction passage 50, that is, through the suction tube 50a and the lateral oil passage 50 b, and discharges the drawn-up oil 23to the first oil supply passage 51 and the second oil supply passage 52.The oil discharged to the first oil supply passage 51 is supplied to thelubricated portion of the engine E, as described above.

Meanwhile, the oil supplied to the second oil supply passage 52sequentially passes through the inlet oil passage 52 a and the orifice57; ascend through the vertical hole 52 b of the upper output shaft 20 ato go out of the horizontal hole 52 c; enters the transmission cover 29while lubricating the thrust needle bearing 48; and then flows into thecirculation circuit 28 from the outer peripheral side of the turbinerunner 26.

The pump impeller 25 driven by the drive plate 31 causes the oil in thecirculation circuit 28 to circulate, as shown by the arrows, therebytransmitting the rotational torque of the pump impeller 25 to theturbine runner 26 to drive the output shaft 20. At this time, if thetorque is amplified between the pump impeller 25 and the turbine runner26, the reaction force due to the amplification is borne by the stator27, which is fixed there by the locking operation of the free wheel 38.Such a torque amplifying effect of the torque converter T stronglydrives the propeller 2, thereby effectively improving start andacceleration of a ship.

After the amplification, the stator 27 rotates in the same directiontogether with the pump impeller 25 and the turbine runner 26 due to thereversal in direction of the torque which the stator 27 receives, whilecausing the freewheel 38 to run idle.

After being used at the circulation circuit 28, the oil runs down thecylindrical oil passage 54 a while lubricating the thrust needle bearing47 above the hub of the pump impeller 25, and enters the valve chamberof the pressure response valve 58 from the outlet oil passage 54 b.

The oil having entered the valve chamber 60 exerts a pressure to pressthe valve body 61 of the pressure response valve 58 against the set loadof the valve spring 63, whereby the valve body 61 is opened to open thevalve hole 62, so that the oil returns from the valve chamber 60 throughthe valve hole 62 into the oil suction passage 50 or the oil tank 22. Inthis way, the oil circulates between the circulation circuit 28 of thetorque converter T and the oil tank 22 arranged below the torqueconverter T through the second oil supply passage 52 and the second oilreturn passage 54. Therefore, it is possible to downsize the torqueconverter T, and promote the cooling of the circulating oil to preventdegradation of the oil.

In particular, since the oil tank 22 arranged below the torque converterT is separated from the engine E, the oil tank 22 is not much heated bythe engine E, the oil tank 22 can have a relatively large capacitywithout any interference by the engine E and the torque converter T, andthus can increase the amount of oil flowing into the circulation circuit28, thereby further promoting the cooling of the circulating oil.Further, the engine E, the torque converter T, and the oil tank 22 aresequentially arranged from top to bottom, thereby downsizing theoutboard engine system O or the vertical power unit including thesecomponents.

Further, because the torque converter T having a relatively heavy weightand the output shaft 20 are arranged so as to be offset by the certaindistance e from the crankshaft 17 toward the cylinder block 18, thecenter of gravity of the outboard engine system O or the vertical powerunit can be close to the central part of the engine E in the front-reardirection, thereby facilitating the handling of the outboard enginesystem O or the vertical power unit. Especially in the case of theoutboard engine system O, the arrangement in which the outboard enginesystem O or the vertical power unit is offset from the crankshaft 17toward the cylinder block 18 means that the crankshaft 17 is offset fromthe torque converter T and the output shaft 20 toward the swivel shaft6. That is, the center of gravity of the engine E correspondingly getscloser to the swivel shaft 6, thereby providing a smooth steering of theoutboard engine system O about the swivel shaft 6.

Furthermore, the transmission device 81 providing a connection betweenthe crankshaft 17 and the torque converter T that are arranged to beoffset from each other is disposed in the oil reservoir case 24, whichreceives, through the opening 66 at the bottom portion of the crankcase19, the oil having lubricated the respective components of the engine E.Therefore, the transmission device 81 is lubricated by the oil in theoil reservoir case 24, thereby securing the durability of thetransmission device 81. The oil received in the oil reservoir case 24flows through the through holes 67 down onto the mount case 11 and theamount of the oil residing in the oil reservoir case 24 is small,thereby suppressing the agitation of the oil because of the transmissiondevice 81 to minimize the power loss. The amount of the oil residing inthe oil reservoir case 24 can be set by selection of the inner diameterof the through holes 67.

The oil having flowed down, from the oil reservoir case 24 through thethrough holes 67, onto the mount case 11 returns to the oil tank 22through the opening 68. Because the through holes 67 are provided awayfrom the torque converter T toward the outer periphery, and the oil inthe oil reservoir case 24 passes through the through holes 67, thecontact of the oil with the outer peripheral surface of the torqueconverter T is avoided, thereby avoiding needless agitation and splashof the oil to minimize the power loss.

The oil discharged from the oil pump 41 for lubricating the engine E isalso supplied to the circulation circuit 28, which eliminates anyaddition/expansion of the oil tank 22 and the oil pump 41 for supplyingthe oil to the circulation circuit 28, thereby avoiding an increase ofsize and complication of the outboard engine system O.

The elongated output shaft 20 is divided into two portions, that is, theupper output shaft 20 a and lower output shaft 20 b which areretractably spline-connected to each other. The upper output shaft 20 ais coupled to the stator shaft 37 in the axial direction via the lowerball bearing 44 and the stopper collar 74. Therefore, the torqueconverter T, the bearing bracket 14, the pump cover 42, and the upperoutput shaft 20 a are compactly incorporated into a single unit as avertical power transmission without any interference by the lower outputshaft 20 b, thereby facilitating assemblability of the vertical powertransmission and mountability of the vertical fluid power transmissionto the outboard engine system O.

Further, if the gear case 12 is separated from the extension case 10 formaintenance of the forward-reverse shifting gear mechanism 21 forexample, the lower output shaft 20 b can be separated downward togetherwith the gear case 12 while the upper output shaft 20 a is remained onthe torque converter T side, by pulling the spline shaft 80 of the loweroutput shaft 20 b out of the spline hole 77 of the upper output shaft 20a. Therefore, it is possible to easily perform the maintenance of theforward-reverse shifting gear mechanism 21, and further avoiddisassembly of the vertical fluid power transmission to easilyreassemble the gear case 12 into the system.

Furthermore, since the bottom wall of the vertical hole 52 as a part ofthe second oil supply passage 52 b, that is, the plug 78 is screwed intothe upper output shaft 20 a of the vertical fluid power transmission,the oil is prevented from flowing out of the vertical hole 52 b andgoing downward of the upper output shaft 20 a. In this case, althoughthe bottom wall of the vertical hole 52 b may be integrally formed withthe upper output shaft 20 a, the vertical hole 52 b, the plug hole 76,and the spline hole 77 are arranged to axially pass through the upperoutput shaft 20 a if the plug 78 is used. Therefore, after processing ofthese holes, washing can advantageously reliably prevent cut chips fromresiding in these holes.

The same is true in the case where the engine E and the torque converterT are removed from the mount case 11, which facilitates maintenance ofthese components.

Moreover, the engine E is mounted to the mount case 11 via the bearingbracket 14 supporting the pump shaft 39 of the torque converter T, theupper distance member 15 connected to the upper end of the bearingbracket 14 to surround the torque converter T, and the lower distancemember 13 connected to the lower end of the bearing bracket 14.Therefore, it is possible to easily mount the engine E to the mount case11 without any interference by the torque converter T, thereby providingan excellent assemblability.

The oil pump 41 is attached to the pump housing 40 formed on the lowersurface of the bearing bracket 14 and holds the pump cover 42.Therefore, the bearing bracket 14 supports not only the torque converterT but also the oil pump 41, thereby simplifying the support structure ofthe oil pump 41.

When the operation of the engine E is terminated, also the operation ofthe oil pump 41 is terminated, so that in the pressure response valve58, the pressure of the valve chamber 60 is decreased and the valve body61 is closed by the set load of the valve spring 63. This causes theoutlet oil passage 54 b to enter the blocked state, and prevents the oilfrom flowing from the circulation circuit 28 of the torque converter Tinto the oil tank 22, thereby keeping the circulation circuit 28 filledwith the oil. Therefore, it is possible to enhance the responsiveness ofoperation of the torque converter T.

Because a part of the second oil supply passage 52 is the vertical hole52 b which is formed at the central portion of the upper output shaft 20a and whose upper end communicates with the circulation circuit 28, thestructure of the second oil supply passage 52 can be simplified.Further, when the engine E is not operated, the vertical hole 52 bprevents the oil from flowing back from the circulation circuit 28 intothe oil pump 41.

The present invention is not limited to the above described embodiment,and various modifications in design can be made without departing fromthe subject matter of the present invention. For example, the oil tank22 may be divided into a section for storing working oil for the torqueconverter T and a section for storing lubrication oil for the engine E,and oil suitable for each purpose is stored in each section. Further,the power may be input from the engine E through a reduction gear intothe torque converter T, and the power may be transferred from the torqueconverter T through the reduction gear into the output shaft 20.

1. A vertical power unit comprising: an engine which has a verticallyarranged crankshaft having a center axis; a vertically arranged outputshaft provided below the crankshaft; and a torque converter which isdisposed between the crankshaft and the output shaft, and transmitspower from the crankshaft to the output shaft, the torque converterhaving a center axis, a pump impeller, a turbine runner, and a statordisposed between the pump impeller and the turbine runner; wherein thecenter axis of the torque converter is arranged so as to be offset fromthe center axis of the crankshaft toward a cylinder block of the engine;a transmission device is provided between the crankshaft and the torqueconverter; and the output shaft is arranged coaxially with the torqueconverter.
 2. The vertical power unit according to claim 1, furthercomprising an oil reservoir case provided between the transmissiondevice and the torque converter to receive a lubrication oil flowingdown from the engine for lubricating the transmission device.
 3. Thevertical power unit according to claim 2, further comprising: an oiltank provided below the torque converter to store oil which is suppliedto the engine; and an oil passage provided apart from the torqueconverter so as to return the oil in the oil reservoir case to the oiltank.
 4. An outboard engine system comprising: a casing coupled to aswivel case via a swivel shaft; an engine mounted in an upper part ofthe casing such that a crankshaft of the engine is vertically arrangedand a cylinder block of the engine faces in a direction opposite to theswivel shaft, the crankshaft having a center axis; a torque converterhaving a center axis, a pump impeller, a turbine runner, and a statordisposed between the pump impeller and the turbine runner; a verticallyarranged output shaft connected to the crankshaft through the torqueconverter; a horizontally arranged propeller shaft provided below theoutput shaft; and a forward-reverse shifting gear mechanism forproviding a connection between the output shaft and the propeller shaft;the torque converter, the output shaft, the propeller shaft and theforward-reverse shifting gear mechanism being disposed in the casing,wherein the center axis of the torque converter is arranged so as to beoffset from the center axis of the crankshaft toward a cylinder block ofthe engine; a transmission device is provided between the crankshaft andthe torque converter; and the output shaft is arranged coaxially withthe torque converter.